Involuntary movements have often been difficult to classify clinically. Clinical and physiological analysis of a continuing series of patients has led to new classifications and pathophysiological insights.Dystonias have been the focus of our recent work. Task specific focal dystonias of the hands such as writer's cramp and pianist's cramp have been analyzed and a number of physiological characteristics have been defined. There appears to be diminished ability to control the fingers independently and gating of somatosensory evoked potentials with voluntary movement is abnormal. The spasms themselves have been characterized into different patterns.Abnormalities of the blink reflex have been identified in dystonic disorders. We have verified this in a number of our own patients and are now applying this test to the patients with focal hand cramps. These patients have also been studied with a specific test for analysis of reciprocal inhibition in the arm. Reciprocal inhibition is diminished in the arm which shows the focal dystonia, but not in the arm which is not dystonic. This finding of a physiological abnormality in focal hand cramps is the most objective laboratory abnormality seen in these patients, and is now the strongest evidence against the psychogenic origin on the disorder. Since trauma often precedes focal dystonia, we are evaluating the influence of pain on reciprocal inhibition. We are developing other tools for the evaluation of the motor system in patients with movement disorders including the electrocutaneous reflex (ECR) and perioral reflexes.